Is there an alternative for unordered_map?

I have a struct my_struct like below.
struct my_struct {
unsigned int a, b;
std::string s1, s2;

I need to map/retrieve a vector/list of this struct against another std::string (usually large, coming from some variant of mangled function names) as key.

Currently, I am using std::unordered_map<string, vector> as the data structure. (The keys need not be sorted).

Is there a better alternative for the unordered_map<> from LLVM’s data structures?

LLVM has a data structure called StringMap which is optimized for using strings as keys. You can find more details about it in the Programmer’s Manual.

For the value, LLVM has a SmallVector that’s optimized, as the name implies, for small lists. Again more information in the Programmer’s Manual.


Note that StringMap is copying the string into the keys of the map, while a DenseMap<StringRef, XYX> would be used when the string are allocated outside of the map.


Thank you both of you.
I will check them out.

Note that, normally, using llvm::SmallVector in the element type of a data structure is something you should be cautious about because many data structures periodically need to reallocate buffers and move elements as the data structure grows, and llvm::SmallVector can be relatively expensive to move this way. However, this is specifically not a problem with the elements of llvm::StringMap, because pointers to the entries of an llvm::StringMap are stable across mutations of the map (that don’t destroy that specific entry).